The major objective of this research is elucidation of the regulation of fatty acid biosynthesis in mammals. Particular emphasis is placed on brain, liver and adipose tissue and on regulation in these tissues during development. Regulation is delineated at the enzymatic level, and the system studied in most detail is the critical multienzyme complex, fatty acid synthetase (FAS). Studies are carried out on tissues in vivo and on cells in culture. Over the next year we propose to continue our in vivo studies to include: (1) elucidation of the role of thyroid hormone in regulation of FAS and acetyl-CoA carboxylase in developing mammalian brain, and (2) purification and characterization of FAS of mammalian brain, with special emphasis on molecular and kinetic properties, aspects of prosthetic group metabolism, and primer specificity. Relevant to the problem of primer preference, we will study the beta-reductive enzymes that are responsible for the synthesis of the preferred primer, butyryl-CoA. We will also continue our studies of FAS and acetyl-CoA carboxylase and lipid synthesis in cultured cells of neural origin. Long-term regulation will be studied with regard to a variety of hormones and related compounds, cyclic mononucleotides and drugs, especially phenobarbital. Mechanisms of the adaptive changes in enzyme content observed during long-term regulation will be elucidated. Short-term regulation of lipid synthesis will also be studied in more detail, and the site of regulation by lipid defined. Long and short-term regulation in neuroblastoma cells will be studied with regard to neuronal differentiation, hormonal factors, nerve growth factor, cyclic mononucleotides and drugs. BIBLIOGRAPHIC REFERENCES: Volpe, J. and Marasa, J.: Hormonal regulation of fatty acid synthetase, acetyl-CoA carboxylase and fatty acid synthesis in mammalian adipose tissue and liver. Biochim. Biophys. Acta 380:454, 1975. Volpe, J.J. and Marasa, J.C: Regulation of hepatic fatty acid synthetase in the obese hyperglycemic mutant mouse. Biochim. Biophys. Acta., In Press, l975.